1. Field of the Invention
The present invention relates to a terminal structure, a printed wiring board, a module substrate, and an electronic device.
2. Related Background Art
An electronic device is constructed using a package substrate fabricated by connecting a module substrate with various electronic components thereon to a motherboard or the like. Normally, such a module substrate is connected to the motherboard by joining terminals on a surface thereof and conductor portions of the motherboard by soldering, whereby the electronic components mounted on the module substrate come to function.
From the viewpoint of ensuring reliability of the electronic device as described above, the connection between the module substrate and the motherboard and the connection between the electronic components and the module substrate are required not to break easily. For this reason, the module substrate or the like used in connection to the motherboard and the terminals forming the connection part thereof are required to demonstrate excellent solder joint strength evaluated by a solder ball pull test and excellent drop resistance evaluated by a drop test.
Incidentally, for joining of the electronic components in the module substrate, electroless gold plating is sometimes carried out after execution of electroless nickel plating as a surface treatment on a conductor part at each joint location. It is, however, known that the execution of the electroless gold plating can result in corroding the surface of nickel with precipitation of gold and thereby degrading soldering performance and wire bonding performance. For this reason, it is proposed to form a protecting layer of electroless nickel film or to dispose an electroless nickel film with high corrosion resistance between electroless nickel film and electroless gold plated film (e.g., cf. Japanese Patent Application Laid-open No. 2008-177261).